BRUSSELS, Oct 20 (Reuters) - Germany's transport minister said on Thursday that the European Union has no legal case against it over its policing of car emissions rules, ramping up a blame game between Brussels and EU nations after the Volkswagen scandal.

Alexander Dobrindt told Reuters he wants a debate at a December meeting with EU counterparts on how to revise an EU law which he says is too vague about emission controls outside laboratory tests that do not reflect real road driving conditions.

"In my view, that (EU legal threat) is very far fetched," he told Reuters after appearing before a European Parliament inquiry committee investigating regulatory negligence in overseeing Europe's second biggest industry.

"I am finding one by one that member states are carrying out their tests and there is growing understanding of the need to change rules."

Europe's Industry Commissioner Elzbieta Bienkowska has said EU law is clear on banning defeat devices to tweak the amount of health-harming nitrogen oxide (NOx) spewed out by diesel engines and promised formal infringement procedures against EU member states for failing to enforce it.

When EU regulators judge a member state is improperly applying the law, it can order corrective action. In case of inaction, the case will go to court. In rare cases and after a process that can take years, the EU may levy fines.

In response to criticism, the EU executive says it will issue guidelines in December on how authorities should rule on carmakers' use of a legal clause which allows for the devices if they are needed to protect engines.

"Currently it is very far reaching, very open to interpretation," Dobrindt told EU lawmakers, saying making mandatory use of state of the art technology would close the legal loophole.

He pointed to General Motors division Opel's throttling back of exhaust treatment at temperatures below 17 degrees centigrade on certain models as a case in which doubt remains as to whether this is justified to safeguard engines.

While a German investigation has led to the voluntary recall of 630,000 Porsche, Volkswagen Opel, Audi and Mercedes vehicles to fix emissions-management software, Germany has said Italy's Fiat Chrysler FCHA.MI is the only one other than VW to break the law.

Germany has asked the European Commission to mediate in its dispute with Italian type-approval authorities over the issue, and Dobrindt called for a body to help resolve such disagreements in the future.

The EU executive proposed new rules to improve market surveillance over the car industry earlier this year, including handing power to member states to recall cars approved by other members of the 28-nation bloc. (Reporting by Alissa de Carbonnel and Andreas Kröner; Editing by Ruth Pitchford)

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